Particle Scattering Induced Orbital Angular Momentum Spectrum Change of Vector Bessel–Gaussian Vortex Beam

Abstract

In this paper, we obtain the intensity and phase distributions of the scattering and external fields of a vector Bessel–Gaussian vortex beam in the far-field region after being scattered by a particle. In our analysis, we use the Generalized Lorenz–Mie theory (GLMT) and the angular spectrum decomposition method (ASDM). The orbital angular momentum (OAM) spectra of the fields are analyzed by using the spiral spectrum expansion method, which is a frequently used tool for studying the propagation of vortex beams in turbulent atmospheres. Both scattered and external fields show a significant difference in spiral spectra for particles with different characteristic parameters, such as the size and complex refractive index. We also examine sampling the phase along with a circle and show that it is unable to fully express the information of the fields. This study can provide a theoretical basis for the inversion of characteristic parameters of the Bessel–Gaussian vortex beam and spherical particle by OAM spectra with applications in remote sensing engineering.

Scattering Field Intensity and Orbital Angular Momentum Spectral Distribution of Vortex Electromagnetic Beams Scattered by Electrically Large Targets Comprising Different Materials

“…After interacting with the target, the phase distribution of the scattering field changes. To display the distribution and variation of the spiral phase visually, the OAM spectral distribution of the scattering field is calculated using the spiral spectral expansion [38,40]. Any field distribution can be expanded into the superposition of multiple spiral harmonics:…”

“…Recently, Shi and her co-workers discussed a difference-sampling method that covered the entire region and line path along a specific radius. They found that, unlike sampling along a certain radius, whole-region sampling could accurately represent the particle scattering results [40]. In a previous study, we investigated the scattering characteristics of on-and off-axis vortex beams scattered by differently shaped targets.…”

“…The coherent superposition of the scattering fields causes the phase of the scattering electric field to become more complex and variable. Unlike the simply shaped particles in [40], the targets in this study require that the OAM spectrum corresponding to different radii be described in detail. Use of the OAM spectrum description method in [40] may result in significant information loss.…”

“…Unlike the simply shaped particles in [40], the targets in this study require that the OAM spectrum corresponding to different radii be described in detail. Use of the OAM spectrum description method in [40] may result in significant information loss. Therefore, we adopted a method to calculate the scattering OAM spectral distribution for different radii.…”

Generalized Lorenz-Mie theory and simulation software for structured light scattering by particles

“…A critical characteristic of Bessel-type and other vortex beams is OAM. Shi et al [79] studied the OAM spectrum of vector BG beams after particle scattering, as shown in Figure 10. This research provides valuable insights into changes in OAM characteristics of structured light following microparticle scattering.…”